The Mozilla build VM

A virtual build environment for Firefox

April 7, 2014

Note: This post might be outdated as it has been turned into an MDN page.
Please refer to the MDN page for the latest information about the Firefox
Developer VM. It will also tell you the correct checksum to compare to after
downloading.

If you ever wondered what contributing to Firefox feels like but you never had
the time to read and follow through our
instructions to setup a build environment
or wanted to avoid screwing around with your precious system then this might
be for you.

This article will guide you through a small list of steps that in the end
will leave you with a virtual machine ready to modify and build your own
development version of Firefox.

I hope this will be valuable to novice programmers that do not have a full
C++ development environment at hand as well as to the more experienced
folks with little time and lots of curiosity.

Install VirtualBox

Note: The Open Virtualization Format (OVF)
is supported by other Virtualization Environments such as VMWare, etc. You
can use those if already installed instead of VirtualBox.

Go to the VirtualBox Downloads
page and download the latest version available for your operating system.
Should you already have VirtualBox installed then please ensure you are running
the latest version by checking for updates before continuing.

Download the Firefox Build Environment

Now is the time to download the virtual machine containing our development
environment ready to modify and build Firefox. You can get it here:

Downloading ~2.8 GB might take a while if you are on a slow connection, sorry.

Set up the virtual machine

Once the image has been downloaded you can double-click the .ova file
and import the new virtual machine into VirtualBox. Please give it at least
2048MB of RAM (4096MB if you can) and the same number of processors that your
host machine has available. Building Firefox takes up a lot of resources and
you want it to build as fast as possible.

Now that your virtual machine is ready, boot it and wait for the Ubuntu desktop
to be shown. A terminal will pop up automatically and do some last steps before
we can get started. After a successful installation Sublime 2 should start
automatically.

Note: Should you ever need root credentials, use “firefox-dev” as the
password. If you want to change your Language and Keyboard settings then
follow the instructions on
How to change the UI Language in Ubuntu.

Build Firefox

Click Tools > Build to start the process. This might take a long time
depending on the features of your host machine, please be patient. You can
watch the build progress in the text editor’s console at the bottom. Once the
build has finished you can use Tools > Run to start your custom Firefox
build and check that everything works as expected.

Note: if you want to switch from an optimized to a debug build then
choose Tools > Build System > Firefox (Debug) and hit Tools > Build
again to start a debug build.

Now what?

You successfully built Firefox for the first time and wonder what’s next? How
about picking a small bug for a start, contribute code and get your changes
shipped to half a billion people? If that sounds compelling then take a look
at Bugs Ahoy! and find something to
work on that sounds interesting to you.

If you are interested in digging deeper into the build system or the version
control system, or want to know more about how to create your first patch and
post it to our bug tracker then take a look at our
Code Firefox Lessons.

I would love to hear your feedback about the Firefox Build Environment!
Please tell me what can be improved and what you would like to see in the next
version. Do not hesitate to drop me a mail should you have a more detailed
opinion.